#include<stdio.h>
int Fib(int n)
{
	if (n == 1)
		return 1;
	else
		return Fib(n - 1) + Fib(n - 2);
}
int main()
{
	int n;
	scanf_s("%d", &n);
	printf("%d\n", Fib(n));
	return 0;
}